With increasing automation in the roving field, new requirements are constantly having to be met as to the shape of the flyer to satisfy the needs of automating bobbin replacement.
Bobbin replacement can be effected by, for example, lowering of the bobbin rail together with the full bobbins which extend upwardly from the bobbin supports thereon, thereby displacing the full bobbins out of the region of the flyers. The full bobbins are then gripped at their free core sleeve ends and withdrawn from the machine by a bobbin pick-up system which is fed into the roving frame at the level of the bobbin rail.
In order to ensure that the pressing finger with its pressing-finger plate will rest against the core sleeve surface after insertion of the empty core sleeve, it is known from German patent 30 04 165 to provide a roving tube on the flyer arm carrying the pressing finger which defines a cylindrical space in which a cylindrical torsion spring is received which surrounds the roving tube and is connected at one end with the roving tube and at the other end with the flyer arm. This spring effects a pressing of the pressing finger against the core sleeve.
A disadvantage with this approach, however, is that the spring maintains a constant pressing force upon the sleeve and the roving wound thereon upon winding of the sleeve with the roving and this has an increasingly negative effect on bobbin formation with increasing bobbin diameter and can be detrimental to the material wound up. In addition, the shape of the pressing finger and the pressing-finger plate must satisfy special requirements and special deflecting skids and abutments must be provided in order to enable an automatic bobbin replacement.
German patent document 195 43 716 A1 describes flyers for roving frames which have pressing fingers comprised of pressing-finger rods or bars and pressing-finger arms carrying pressing-finger plates. The pressing-finger rod or bar which lies outside a pivot axis, can be swung by an actuating element effective transverse to the pivot axis so that the pressing finger can be pivoted into an outwardly swung position and can be held in this position. The pressing finger can be swung outwardly sufficiently that the full bobbin can be removed from the rotation region on the flyer. To enable the pressing finger to flip back for automatic incipient spinning, the abutment on the flyer arm must be so provided that the center of gravity of the respective abutment and pressing finger is so oriented that it will ensure an inward swing of the pressing finger against the bobbin upon the initiation of spinning. Reference may also be had to U.S. Pat. No. 5,657,623 with respect to the actuation elements which engage such pressing-finger bars.
With these known systems which provide for wide opening of the pressing finger, the pressing finger can remain in its outwardly swung position during incipient spinning. The reason for this is, above all, that the abutment on the flyer arm is configured as a rigid abutment. During the hard positioning of the pressing finger in the outwardly swung position, wear of contacting parts tends to be pronounced and, as a consequence there may be a change in the location of the outwardly swung position of the pressing finger during machine operation. Because of this wear, the center of gravity of the pressing finger may change with time and during start-up of the spinning process. The pressing finger may not automatically swing back against the core sleeve and the initial turns of the roving on the bobbin. The undeniable result is that because of the close spacing of the flyers (diagonal spacing of the flyer pitch), especially in the case of large bobbin sizes, the pressing fingers may engage in one another and thereby be damaged.